Field of the Invention
The present invention relates to a liquid ejection apparatus, which performs printing by ejecting liquid on a printing medium, represented by an inkjet printing scheme. More specifically, the invention relates to a page wide type liquid ejection head in which a plurality of print element boards is disposed across a page width, and a liquid ejection apparatus mounted with the page wide type liquid ejection head.
Description of the Related Art
There is a known liquid ejection apparatus mounted with a page wide type liquid ejection head in which a plurality of print element boards is disposed across a page width. An elongated liquid ejection head developed for commercial printing is mounted in a liquid ejection apparatus corresponding to an example of the known liquid ejection apparatus. In addition, ink is circulated between an ink tank and a liquid ejection head in a liquid ejection apparatus corresponding to another example thereof.
In such a liquid ejection apparatus, a pressure difference may be generated in a pressure applied to ink adjacent to each ejection opening in some cases. For example, a large amount of ink is supplied to the elongated liquid ejection head, and thus a pressure difference is easily generated around each ejection opening depending on printing duties. In addition, for example, in a circulation-type liquid ejection apparatus, a pressure variation generated when a circulation pump pulses may affect a pressure difference around each ejection opening in some cases.
In a case where printing is performed in a state in which a pressure difference is generated around each ejection opening, the volume of ink drops ejected from each ejection opening is non-uniform, which causes unevenness in density in a printed image to degrade an image quality. In order to avoid this phenomenon, U.S. Pat. No. 7,922,312 and Japanese Patent No. 03606282 have proposed a liquid ejection apparatus in which a pressure adjustment mechanism is provided in an ink supply path that allows communication between an ink tank and a liquid ejection head to adjust a pressure applied to ink adjacent to each ejection opening.